1. Field of the Invention
The present invention relates to a surface emitting laser device.
2. Description of the Related Art
In recent years, a surface emitting laser device has actively been researched. The surface emitting laser has advantages such as being easily integrated and arrayed and having superior coupling efficiency with an external optical system.
Accordingly, the surface emitting laser device is expected to be applied to the fields such as communications, electrophotography, and sensing. In particular, the surface emitting laser device has already been put to practical use in a communication field such as infrared-ray short range communications.
There are several kinds of surface emitting lasers. As a kind of them, there is a laser device realizing a surface emitting function by resonating light in a direction parallel to a substrate to take out oscillated laser light by diffracting the laser light into a direction perpendicular to the substrate.
As such a diffraction type surface emitting laser, a first patent document (Japanese Patent Application Laid-Open No. 2000-332351) discloses an invention using a second-order diffraction effect of a two-dimensional photonic crystal.
In this invention, the photonic crystal is introduced in the neighborhood of the active layer of a semiconductor laser, and the light emitted in the active layer is oscillated within a plane by the second-order diffraction effect of the photonic crystal.
Then, the surface emitting laser is configured to take out the oscillated laser light into a direction perpendicular to the plane by the first-order diffraction of the same photonic crystal.
The development of a surface emitting laser having further higher performance has strongly been desired recently, and the aforesaid related art grating surface emitting laser device disclosed in the first patent document also has room for further improvement in the points of the degree of freedom of the design of the laser and the light emission efficiency thereof.